The purpose of this study is development of a new design method for competitive swimwear by numerical simulation. Biaxial tensile loading tests were conducted to obtain the mechanical characteristics of competitive swimwear. The fabrics of competitive swimwear consist of chemical fiber. From biaxial tensile loading test results, the fabric has anisotropy and the stiffness of the fabric shows hardening along with the increase of stretch. An anisotropic hyperelastic model was applied to the reproduction of mechanical characteristics of swimwear. Finite element simulation of tensile loading tests was conducted to show the applicability of the anisotropic hyperelastic model to competitive swimwear. The results of the simulation showed good agreement with that of tensile loading test. FE simulation of the pressure using a cylinder model was conducted to show the applicability of our design method to competitive swimwear. The results of the simulation showed good agreement with that of pressure test in a design range of competitive swimwear. Finally, new design method using a displacement field of CG model was proposed.